Laser machining nozzles are disclosed, for example, in U.S. Pat. No. 6,423,928 B1.
According to the prior art, during fusion cutting (e.g. of VA steel), the orifice diameter of a laser machining nozzle in the form of a hole-type nozzle needs to be enlarged as the sheet thickness to be processed increases. For that reason, increasingly high gas pressures are needed. But increasing gas pressures mean an increasing gas density in the cutting gap, resulting in an increased probability of plasma formation. The plasma threshold is dependent inter alia also on the beamed-in power density (an increase in power density or processing temperature increases plasma) and the focal position (a higher focal position increases plasma), and represents a constraint on the quality of the fusion cut.
When cutting thick sheets, better cut edge qualities can be achieved if the cutting gas pressure is reduced. However, this is always associated with the formation of a distinct burr.